Question 19M.2.HL.TZ1.a.ii
| Date | May 2019 | Marks available | [Maximum mark: 1] | Reference code | 19M.2.HL.TZ1.a.ii |
| Level | HL | Paper | 2 | Time zone | TZ1 |
| Command term | Outline | Question number | a.ii | Adapted from | N/A |
The moon Phobos moves around the planet Mars in a circular orbit.
Outline why this force does no work on Phobos.
[1]
the force/field and the velocity/displacement are at 90° to each other OR
there is no change in GPE of the moon/Phobos ✔
Some candidates connected the idea that the gravitational force is perpendicular to the velocity (and hence the displacement) for the mark. It was also allowed to discuss that there is no change in gravitational potential energy, so therefore no work was being done. It was not acceptable to simply state that the net displacement over one full orbit is zero. Unfortunately, some candidates suggested that there is no net force on the moon so there is no work done, or that the moon is so much smaller so no work could be done on it.
